1 /* Control flow optimization code for GNU compiler.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
22 /* This file contains optimizer of the control flow. The main entrypoint is
23 cleanup_cfg. Following optimizations are performed:
25 - Unreachable blocks removal
26 - Edge forwarding (edge to the forwarder block is forwarded to it's
27 successor. Simplification of the branch instruction is performed by
28 underlying infrastructure so branch can be converted to simplejump or
30 - Cross jumping (tail merging)
31 - Conditional jump-around-simplejump simplification
32 - Basic block merging. */
37 #include "hard-reg-set.h"
38 #include "basic-block.h"
41 #include "insn-config.h"
50 /* cleanup_cfg maintains following flags for each basic block. */
54 /* Set if life info needs to be recomputed for given BB. */
56 /* Set if BB is the forwarder block to avoid too many
57 forwarder_block_p calls. */
58 BB_FORWARDER_BLOCK
= 2
61 #define BB_FLAGS(BB) (enum bb_flags) (BB)->aux
62 #define BB_SET_FLAG(BB, FLAG) \
63 (BB)->aux = (void *) (long) ((enum bb_flags) (BB)->aux | (FLAG))
64 #define BB_CLEAR_FLAG(BB, FLAG) \
65 (BB)->aux = (void *) (long) ((enum bb_flags) (BB)->aux & ~(FLAG))
67 #define FORWARDER_BLOCK_P(BB) (BB_FLAGS (BB) & BB_FORWARDER_BLOCK)
69 static bool try_crossjump_to_edge
PARAMS ((int, edge
, edge
));
70 static bool try_crossjump_bb
PARAMS ((int, basic_block
));
71 static bool outgoing_edges_match
PARAMS ((int,
72 basic_block
, basic_block
));
73 static int flow_find_cross_jump
PARAMS ((int, basic_block
, basic_block
,
75 static bool insns_match_p
PARAMS ((int, rtx
, rtx
));
77 static bool delete_unreachable_blocks
PARAMS ((void));
78 static bool label_is_jump_target_p
PARAMS ((rtx
, rtx
));
79 static bool tail_recursion_label_p
PARAMS ((rtx
));
80 static void merge_blocks_move_predecessor_nojumps
PARAMS ((basic_block
,
82 static void merge_blocks_move_successor_nojumps
PARAMS ((basic_block
,
84 static bool merge_blocks
PARAMS ((edge
,basic_block
,basic_block
,
86 static bool try_optimize_cfg
PARAMS ((int));
87 static bool try_simplify_condjump
PARAMS ((basic_block
));
88 static bool try_forward_edges
PARAMS ((int, basic_block
));
89 static edge thread_jump
PARAMS ((int, edge
, basic_block
));
90 static bool mark_effect
PARAMS ((rtx
, bitmap
));
91 static void notice_new_block
PARAMS ((basic_block
));
92 static void update_forwarder_flag
PARAMS ((basic_block
));
94 /* Set flags for newly created block. */
103 BB_SET_FLAG (bb
, BB_UPDATE_LIFE
);
104 if (forwarder_block_p (bb
))
105 BB_SET_FLAG (bb
, BB_FORWARDER_BLOCK
);
108 /* Recompute forwarder flag after block has been modified. */
111 update_forwarder_flag (bb
)
114 if (forwarder_block_p (bb
))
115 BB_SET_FLAG (bb
, BB_FORWARDER_BLOCK
);
117 BB_CLEAR_FLAG (bb
, BB_FORWARDER_BLOCK
);
120 /* Simplify a conditional jump around an unconditional jump.
121 Return true if something changed. */
124 try_simplify_condjump (cbranch_block
)
125 basic_block cbranch_block
;
127 basic_block jump_block
, jump_dest_block
, cbranch_dest_block
;
128 edge cbranch_jump_edge
, cbranch_fallthru_edge
;
131 /* Verify that there are exactly two successors. */
132 if (!cbranch_block
->succ
133 || !cbranch_block
->succ
->succ_next
134 || cbranch_block
->succ
->succ_next
->succ_next
)
137 /* Verify that we've got a normal conditional branch at the end
139 cbranch_insn
= cbranch_block
->end
;
140 if (!any_condjump_p (cbranch_insn
))
143 cbranch_fallthru_edge
= FALLTHRU_EDGE (cbranch_block
);
144 cbranch_jump_edge
= BRANCH_EDGE (cbranch_block
);
146 /* The next block must not have multiple predecessors, must not
147 be the last block in the function, and must contain just the
148 unconditional jump. */
149 jump_block
= cbranch_fallthru_edge
->dest
;
150 if (jump_block
->pred
->pred_next
151 || jump_block
->index
== n_basic_blocks
- 1
152 || !FORWARDER_BLOCK_P (jump_block
))
154 jump_dest_block
= jump_block
->succ
->dest
;
156 /* The conditional branch must target the block after the
157 unconditional branch. */
158 cbranch_dest_block
= cbranch_jump_edge
->dest
;
160 if (!can_fallthru (jump_block
, cbranch_dest_block
))
163 /* Invert the conditional branch. */
164 if (!invert_jump (cbranch_insn
, block_label (jump_dest_block
), 0))
168 fprintf (rtl_dump_file
, "Simplifying condjump %i around jump %i\n",
169 INSN_UID (cbranch_insn
), INSN_UID (jump_block
->end
));
171 /* Success. Update the CFG to match. Note that after this point
172 the edge variable names appear backwards; the redirection is done
173 this way to preserve edge profile data. */
174 cbranch_jump_edge
= redirect_edge_succ_nodup (cbranch_jump_edge
,
176 cbranch_fallthru_edge
= redirect_edge_succ_nodup (cbranch_fallthru_edge
,
178 cbranch_jump_edge
->flags
|= EDGE_FALLTHRU
;
179 cbranch_fallthru_edge
->flags
&= ~EDGE_FALLTHRU
;
180 update_br_prob_note (cbranch_block
);
182 /* Delete the block with the unconditional jump, and clean up the mess. */
183 flow_delete_block (jump_block
);
184 tidy_fallthru_edge (cbranch_jump_edge
, cbranch_block
, cbranch_dest_block
);
189 /* Attempt to prove that operation is NOOP using CSElib or mark the effect
190 on register. Used by jump threading. */
193 mark_effect (exp
, nonequal
)
199 switch (GET_CODE (exp
))
201 /* In case we do clobber the register, mark it as equal, as we know the
202 value is dead so it don't have to match. */
204 if (REG_P (XEXP (exp
, 0)))
206 dest
= XEXP (exp
, 0);
207 regno
= REGNO (dest
);
208 CLEAR_REGNO_REG_SET (nonequal
, regno
);
209 if (regno
< FIRST_PSEUDO_REGISTER
)
211 int n
= HARD_REGNO_NREGS (regno
, GET_MODE (dest
));
213 CLEAR_REGNO_REG_SET (nonequal
, regno
+ n
);
219 if (rtx_equal_for_cselib_p (SET_DEST (exp
), SET_SRC (exp
)))
221 dest
= SET_DEST (exp
);
226 regno
= REGNO (dest
);
227 SET_REGNO_REG_SET (nonequal
, regno
);
228 if (regno
< FIRST_PSEUDO_REGISTER
)
230 int n
= HARD_REGNO_NREGS (regno
, GET_MODE (dest
));
232 SET_REGNO_REG_SET (nonequal
, regno
+ n
);
240 /* Attempt to prove that the basic block B will have no side effects and
241 allways continues in the same edge if reached via E. Return the edge
242 if exist, NULL otherwise. */
245 thread_jump (mode
, e
, b
)
250 rtx set1
, set2
, cond1
, cond2
, insn
;
251 enum rtx_code code1
, code2
, reversed_code2
;
252 bool reverse1
= false;
257 /* At the moment, we do handle only conditional jumps, but later we may
258 want to extend this code to tablejumps and others. */
259 if (!e
->src
->succ
->succ_next
|| e
->src
->succ
->succ_next
->succ_next
)
261 if (!b
->succ
|| !b
->succ
->succ_next
|| b
->succ
->succ_next
->succ_next
)
264 /* Second branch must end with onlyjump, as we will eliminate the jump. */
265 if (!any_condjump_p (e
->src
->end
) || !any_condjump_p (b
->end
)
266 || !onlyjump_p (b
->end
))
269 set1
= pc_set (e
->src
->end
);
270 set2
= pc_set (b
->end
);
271 if (((e
->flags
& EDGE_FALLTHRU
) != 0)
272 != (XEXP (SET_SRC (set1
), 1) == pc_rtx
))
275 cond1
= XEXP (SET_SRC (set1
), 0);
276 cond2
= XEXP (SET_SRC (set2
), 0);
278 code1
= reversed_comparison_code (cond1
, e
->src
->end
);
280 code1
= GET_CODE (cond1
);
282 code2
= GET_CODE (cond2
);
283 reversed_code2
= reversed_comparison_code (cond2
, b
->end
);
285 if (!comparison_dominates_p (code1
, code2
)
286 && !comparison_dominates_p (code1
, reversed_code2
))
289 /* Ensure that the comparison operators are equivalent.
290 ??? This is far too pesimistic. We should allow swapped operands,
291 different CCmodes, or for example comparisons for interval, that
292 dominate even when operands are not equivalent. */
293 if (!rtx_equal_p (XEXP (cond1
, 0), XEXP (cond2
, 0))
294 || !rtx_equal_p (XEXP (cond1
, 1), XEXP (cond2
, 1)))
297 /* Short circuit cases where block B contains some side effects, as we can't
299 for (insn
= NEXT_INSN (b
->head
); insn
!= NEXT_INSN (b
->end
);
300 insn
= NEXT_INSN (insn
))
301 if (INSN_P (insn
) && side_effects_p (PATTERN (insn
)))
306 /* First process all values computed in the source basic block. */
307 for (insn
= NEXT_INSN (e
->src
->head
); insn
!= NEXT_INSN (e
->src
->end
);
308 insn
= NEXT_INSN (insn
))
310 cselib_process_insn (insn
);
312 nonequal
= BITMAP_XMALLOC();
313 CLEAR_REG_SET (nonequal
);
315 /* Now assume that we've continued by the edge E to B and continue
316 processing as if it were same basic block.
317 Our goal is to prove that whole block is an NOOP. */
319 for (insn
= NEXT_INSN (b
->head
); insn
!= NEXT_INSN (b
->end
) && !failed
;
320 insn
= NEXT_INSN (insn
))
324 rtx pat
= PATTERN (insn
);
326 if (GET_CODE (pat
) == PARALLEL
)
328 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
329 failed
|= mark_effect (XVECEXP (pat
, 0, i
), nonequal
);
332 failed
|= mark_effect (pat
, nonequal
);
335 cselib_process_insn (insn
);
338 /* Later we should clear nonequal of dead registers. So far we don't
339 have life information in cfg_cleanup. */
343 /* In case liveness information is available, we need to prove equivalence
344 only of the live values. */
345 if (mode
& CLEANUP_UPDATE_LIFE
)
346 AND_REG_SET (nonequal
, b
->global_live_at_end
);
348 EXECUTE_IF_SET_IN_REG_SET (nonequal
, 0, i
, goto failed_exit
;);
350 BITMAP_XFREE (nonequal
);
352 if ((comparison_dominates_p (code1
, code2
) != 0)
353 != (XEXP (SET_SRC (set2
), 1) == pc_rtx
))
354 return BRANCH_EDGE (b
);
356 return FALLTHRU_EDGE (b
);
359 BITMAP_XFREE (nonequal
);
364 /* Attempt to forward edges leaving basic block B.
365 Return true if successful. */
368 try_forward_edges (mode
, b
)
372 bool changed
= false;
373 edge e
, next
, *threaded_edges
= NULL
;
375 for (e
= b
->succ
; e
; e
= next
)
377 basic_block target
, first
;
379 bool threaded
= false;
380 int nthreaded_edges
= 0;
384 /* Skip complex edges because we don't know how to update them.
386 Still handle fallthru edges, as we can succeed to forward fallthru
387 edge to the same place as the branch edge of conditional branch
388 and turn conditional branch to an unconditional branch. */
389 if (e
->flags
& EDGE_COMPLEX
)
392 target
= first
= e
->dest
;
395 while (counter
< n_basic_blocks
)
397 basic_block new_target
= NULL
;
398 bool new_target_threaded
= false;
400 if (FORWARDER_BLOCK_P (target
)
401 && target
->succ
->dest
!= EXIT_BLOCK_PTR
)
403 /* Bypass trivial infinite loops. */
404 if (target
== target
->succ
->dest
)
405 counter
= n_basic_blocks
;
406 new_target
= target
->succ
->dest
;
409 /* Allow to thread only over one edge at time to simplify updating
411 else if (mode
& CLEANUP_THREADING
)
413 edge t
= thread_jump (mode
, e
, target
);
417 threaded_edges
= xmalloc (sizeof (*threaded_edges
)
423 /* Detect an infinite loop across blocks not
424 including the start block. */
425 for (i
= 0; i
< nthreaded_edges
; ++i
)
426 if (threaded_edges
[i
] == t
)
428 if (i
< nthreaded_edges
)
432 /* Detect an infinite loop across the start block. */
436 if (nthreaded_edges
>= n_basic_blocks
)
438 threaded_edges
[nthreaded_edges
++] = t
;
440 new_target
= t
->dest
;
441 new_target_threaded
= true;
448 /* Avoid killing of loop pre-headers, as it is the place loop
449 optimizer wants to hoist code to.
451 For fallthru forwarders, the LOOP_BEG note must appear between
452 the header of block and CODE_LABEL of the loop, for non forwarders
453 it must appear before the JUMP_INSN. */
454 if (mode
& CLEANUP_PRE_LOOP
)
456 rtx insn
= (target
->succ
->flags
& EDGE_FALLTHRU
457 ? target
->head
: prev_nonnote_insn (target
->end
));
459 if (GET_CODE (insn
) != NOTE
)
460 insn
= NEXT_INSN (insn
);
462 for (; insn
&& GET_CODE (insn
) != CODE_LABEL
&& !INSN_P (insn
);
463 insn
= NEXT_INSN (insn
))
464 if (GET_CODE (insn
) == NOTE
465 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_LOOP_BEG
)
468 if (GET_CODE (insn
) == NOTE
)
474 threaded
|= new_target_threaded
;
477 if (counter
>= n_basic_blocks
)
480 fprintf (rtl_dump_file
, "Infinite loop in BB %i.\n",
483 else if (target
== first
)
484 ; /* We didn't do anything. */
487 /* Save the values now, as the edge may get removed. */
488 gcov_type edge_count
= e
->count
;
489 int edge_probability
= e
->probability
;
493 /* Don't force if target is exit block. */
494 if (threaded
&& target
!= EXIT_BLOCK_PTR
)
496 notice_new_block (redirect_edge_and_branch_force (e
, target
));
498 fprintf (rtl_dump_file
, "Conditionals threaded.\n");
500 else if (!redirect_edge_and_branch (e
, target
))
503 fprintf (rtl_dump_file
,
504 "Forwarding edge %i->%i to %i failed.\n",
505 b
->index
, e
->dest
->index
, target
->index
);
509 /* We successfully forwarded the edge. Now update profile
510 data: for each edge we traversed in the chain, remove
511 the original edge's execution count. */
512 edge_frequency
= ((edge_probability
* b
->frequency
513 + REG_BR_PROB_BASE
/ 2)
516 if (!FORWARDER_BLOCK_P (b
) && forwarder_block_p (b
))
517 BB_SET_FLAG (b
, BB_FORWARDER_BLOCK
);
518 BB_SET_FLAG (b
, BB_UPDATE_LIFE
);
524 first
->count
-= edge_count
;
525 if (first
->count
< 0)
527 first
->frequency
-= edge_frequency
;
528 if (first
->frequency
< 0)
529 first
->frequency
= 0;
530 if (first
->succ
->succ_next
)
534 if (n
>= nthreaded_edges
)
536 t
= threaded_edges
[n
++];
539 if (first
->frequency
)
540 prob
= edge_frequency
* REG_BR_PROB_BASE
/ first
->frequency
;
543 if (prob
> t
->probability
)
544 prob
= t
->probability
;
545 t
->probability
-= prob
;
546 prob
= REG_BR_PROB_BASE
- prob
;
549 first
->succ
->probability
= REG_BR_PROB_BASE
;
550 first
->succ
->succ_next
->probability
= 0;
553 for (e
= first
->succ
; e
; e
= e
->succ_next
)
554 e
->probability
= ((e
->probability
* REG_BR_PROB_BASE
)
556 update_br_prob_note (first
);
560 /* It is possible that as the result of
561 threading we've removed edge as it is
562 threaded to the fallthru edge. Avoid
563 getting out of sync. */
564 if (n
< nthreaded_edges
565 && first
== threaded_edges
[n
]->src
)
570 t
->count
-= edge_count
;
575 while (first
!= target
);
582 free (threaded_edges
);
586 /* Return true if LABEL is a target of JUMP_INSN. This applies only
587 to non-complex jumps. That is, direct unconditional, conditional,
588 and tablejumps, but not computed jumps or returns. It also does
589 not apply to the fallthru case of a conditional jump. */
592 label_is_jump_target_p (label
, jump_insn
)
593 rtx label
, jump_insn
;
595 rtx tmp
= JUMP_LABEL (jump_insn
);
601 && (tmp
= NEXT_INSN (tmp
)) != NULL_RTX
602 && GET_CODE (tmp
) == JUMP_INSN
603 && (tmp
= PATTERN (tmp
),
604 GET_CODE (tmp
) == ADDR_VEC
605 || GET_CODE (tmp
) == ADDR_DIFF_VEC
))
607 rtvec vec
= XVEC (tmp
, GET_CODE (tmp
) == ADDR_DIFF_VEC
);
608 int i
, veclen
= GET_NUM_ELEM (vec
);
610 for (i
= 0; i
< veclen
; ++i
)
611 if (XEXP (RTVEC_ELT (vec
, i
), 0) == label
)
618 /* Return true if LABEL is used for tail recursion. */
621 tail_recursion_label_p (label
)
626 for (x
= tail_recursion_label_list
; x
; x
= XEXP (x
, 1))
627 if (label
== XEXP (x
, 0))
633 /* Blocks A and B are to be merged into a single block. A has no incoming
634 fallthru edge, so it can be moved before B without adding or modifying
635 any jumps (aside from the jump from A to B). */
638 merge_blocks_move_predecessor_nojumps (a
, b
)
644 barrier
= next_nonnote_insn (a
->end
);
645 if (GET_CODE (barrier
) != BARRIER
)
647 delete_insn (barrier
);
649 /* Move block and loop notes out of the chain so that we do not
652 ??? A better solution would be to squeeze out all the non-nested notes
653 and adjust the block trees appropriately. Even better would be to have
654 a tighter connection between block trees and rtl so that this is not
656 if (squeeze_notes (&a
->head
, &a
->end
))
659 /* Scramble the insn chain. */
660 if (a
->end
!= PREV_INSN (b
->head
))
661 reorder_insns_nobb (a
->head
, a
->end
, PREV_INSN (b
->head
));
662 BB_SET_FLAG (a
, BB_UPDATE_LIFE
);
665 fprintf (rtl_dump_file
, "Moved block %d before %d and merged.\n",
668 /* Swap the records for the two blocks around. Although we are deleting B,
669 A is now where B was and we want to compact the BB array from where
671 BASIC_BLOCK (a
->index
) = b
;
672 BASIC_BLOCK (b
->index
) = a
;
677 /* Now blocks A and B are contiguous. Merge them. */
678 merge_blocks_nomove (a
, b
);
681 /* Blocks A and B are to be merged into a single block. B has no outgoing
682 fallthru edge, so it can be moved after A without adding or modifying
683 any jumps (aside from the jump from A to B). */
686 merge_blocks_move_successor_nojumps (a
, b
)
689 rtx barrier
, real_b_end
;
692 barrier
= NEXT_INSN (b
->end
);
694 /* Recognize a jump table following block B. */
696 && GET_CODE (barrier
) == CODE_LABEL
697 && NEXT_INSN (barrier
)
698 && GET_CODE (NEXT_INSN (barrier
)) == JUMP_INSN
699 && (GET_CODE (PATTERN (NEXT_INSN (barrier
))) == ADDR_VEC
700 || GET_CODE (PATTERN (NEXT_INSN (barrier
))) == ADDR_DIFF_VEC
))
702 /* Temporarily add the table jump insn to b, so that it will also
703 be moved to the correct location. */
704 b
->end
= NEXT_INSN (barrier
);
705 barrier
= NEXT_INSN (b
->end
);
708 /* There had better have been a barrier there. Delete it. */
709 if (barrier
&& GET_CODE (barrier
) == BARRIER
)
710 delete_insn (barrier
);
712 /* Move block and loop notes out of the chain so that we do not
715 ??? A better solution would be to squeeze out all the non-nested notes
716 and adjust the block trees appropriately. Even better would be to have
717 a tighter connection between block trees and rtl so that this is not
719 if (squeeze_notes (&b
->head
, &b
->end
))
722 /* Scramble the insn chain. */
723 reorder_insns_nobb (b
->head
, b
->end
, a
->end
);
725 /* Restore the real end of b. */
728 /* Now blocks A and B are contiguous. Merge them. */
729 merge_blocks_nomove (a
, b
);
730 BB_SET_FLAG (a
, BB_UPDATE_LIFE
);
733 fprintf (rtl_dump_file
, "Moved block %d after %d and merged.\n",
737 /* Attempt to merge basic blocks that are potentially non-adjacent.
738 Return true iff the attempt succeeded. */
741 merge_blocks (e
, b
, c
, mode
)
746 /* If C has a tail recursion label, do not merge. There is no
747 edge recorded from the call_placeholder back to this label, as
748 that would make optimize_sibling_and_tail_recursive_calls more
749 complex for no gain. */
750 if ((mode
& CLEANUP_PRE_SIBCALL
)
751 && GET_CODE (c
->head
) == CODE_LABEL
752 && tail_recursion_label_p (c
->head
))
755 /* If B has a fallthru edge to C, no need to move anything. */
756 if (e
->flags
& EDGE_FALLTHRU
)
758 int b_index
= b
->index
, c_index
= c
->index
;
759 /* We need to update liveness in case C already has broken liveness
760 or B ends by conditional jump to next instructions that will be
762 if ((BB_FLAGS (c
) & BB_UPDATE_LIFE
)
763 || GET_CODE (b
->end
) == JUMP_INSN
)
764 BB_SET_FLAG (b
, BB_UPDATE_LIFE
);
765 merge_blocks_nomove (b
, c
);
766 update_forwarder_flag (b
);
769 fprintf (rtl_dump_file
, "Merged %d and %d without moving.\n",
775 /* Otherwise we will need to move code around. Do that only if expensive
776 transformations are allowed. */
777 else if (mode
& CLEANUP_EXPENSIVE
)
779 edge tmp_edge
, b_fallthru_edge
;
780 bool c_has_outgoing_fallthru
;
781 bool b_has_incoming_fallthru
;
783 /* Avoid overactive code motion, as the forwarder blocks should be
784 eliminated by edge redirection instead. One exception might have
785 been if B is a forwarder block and C has no fallthru edge, but
786 that should be cleaned up by bb-reorder instead. */
787 if (FORWARDER_BLOCK_P (b
) || FORWARDER_BLOCK_P (c
))
790 /* We must make sure to not munge nesting of lexical blocks,
791 and loop notes. This is done by squeezing out all the notes
792 and leaving them there to lie. Not ideal, but functional. */
794 for (tmp_edge
= c
->succ
; tmp_edge
; tmp_edge
= tmp_edge
->succ_next
)
795 if (tmp_edge
->flags
& EDGE_FALLTHRU
)
798 c_has_outgoing_fallthru
= (tmp_edge
!= NULL
);
800 for (tmp_edge
= b
->pred
; tmp_edge
; tmp_edge
= tmp_edge
->pred_next
)
801 if (tmp_edge
->flags
& EDGE_FALLTHRU
)
804 b_has_incoming_fallthru
= (tmp_edge
!= NULL
);
805 b_fallthru_edge
= tmp_edge
;
807 /* Otherwise, we're going to try to move C after B. If C does
808 not have an outgoing fallthru, then it can be moved
809 immediately after B without introducing or modifying jumps. */
810 if (! c_has_outgoing_fallthru
)
812 merge_blocks_move_successor_nojumps (b
, c
);
816 /* If B does not have an incoming fallthru, then it can be moved
817 immediately before C without introducing or modifying jumps.
818 C cannot be the first block, so we do not have to worry about
819 accessing a non-existent block. */
821 if (b_has_incoming_fallthru
)
825 if (b_fallthru_edge
->src
== ENTRY_BLOCK_PTR
)
827 bb
= force_nonfallthru (b_fallthru_edge
);
829 notice_new_block (bb
);
831 BB_SET_FLAG (b_fallthru_edge
->src
, BB_UPDATE_LIFE
);
834 merge_blocks_move_predecessor_nojumps (b
, c
);
842 /* Return true if I1 and I2 are equivalent and thus can be crossjumped. */
845 insns_match_p (mode
, i1
, i2
)
846 int mode ATTRIBUTE_UNUSED
;
851 /* Verify that I1 and I2 are equivalent. */
852 if (GET_CODE (i1
) != GET_CODE (i2
))
858 if (GET_CODE (p1
) != GET_CODE (p2
))
861 /* If this is a CALL_INSN, compare register usage information.
862 If we don't check this on stack register machines, the two
863 CALL_INSNs might be merged leaving reg-stack.c with mismatching
864 numbers of stack registers in the same basic block.
865 If we don't check this on machines with delay slots, a delay slot may
866 be filled that clobbers a parameter expected by the subroutine.
868 ??? We take the simple route for now and assume that if they're
869 equal, they were constructed identically. */
871 if (GET_CODE (i1
) == CALL_INSN
872 && !rtx_equal_p (CALL_INSN_FUNCTION_USAGE (i1
),
873 CALL_INSN_FUNCTION_USAGE (i2
)))
877 /* If cross_jump_death_matters is not 0, the insn's mode
878 indicates whether or not the insn contains any stack-like
881 if ((mode
& CLEANUP_POST_REGSTACK
) && stack_regs_mentioned (i1
))
883 /* If register stack conversion has already been done, then
884 death notes must also be compared before it is certain that
885 the two instruction streams match. */
888 HARD_REG_SET i1_regset
, i2_regset
;
890 CLEAR_HARD_REG_SET (i1_regset
);
891 CLEAR_HARD_REG_SET (i2_regset
);
893 for (note
= REG_NOTES (i1
); note
; note
= XEXP (note
, 1))
894 if (REG_NOTE_KIND (note
) == REG_DEAD
&& STACK_REG_P (XEXP (note
, 0)))
895 SET_HARD_REG_BIT (i1_regset
, REGNO (XEXP (note
, 0)));
897 for (note
= REG_NOTES (i2
); note
; note
= XEXP (note
, 1))
898 if (REG_NOTE_KIND (note
) == REG_DEAD
&& STACK_REG_P (XEXP (note
, 0)))
899 SET_HARD_REG_BIT (i2_regset
, REGNO (XEXP (note
, 0)));
901 GO_IF_HARD_REG_EQUAL (i1_regset
, i2_regset
, done
);
911 ? ! rtx_renumbered_equal_p (p1
, p2
) : ! rtx_equal_p (p1
, p2
))
913 /* The following code helps take care of G++ cleanups. */
914 rtx equiv1
= find_reg_equal_equiv_note (i1
);
915 rtx equiv2
= find_reg_equal_equiv_note (i2
);
918 /* If the equivalences are not to a constant, they may
919 reference pseudos that no longer exist, so we can't
921 && (! reload_completed
922 || (CONSTANT_P (XEXP (equiv1
, 0))
923 && rtx_equal_p (XEXP (equiv1
, 0), XEXP (equiv2
, 0)))))
925 rtx s1
= single_set (i1
);
926 rtx s2
= single_set (i2
);
927 if (s1
!= 0 && s2
!= 0
928 && rtx_renumbered_equal_p (SET_DEST (s1
), SET_DEST (s2
)))
930 validate_change (i1
, &SET_SRC (s1
), XEXP (equiv1
, 0), 1);
931 validate_change (i2
, &SET_SRC (s2
), XEXP (equiv2
, 0), 1);
932 if (! rtx_renumbered_equal_p (p1
, p2
))
934 else if (apply_change_group ())
945 /* Look through the insns at the end of BB1 and BB2 and find the longest
946 sequence that are equivalent. Store the first insns for that sequence
947 in *F1 and *F2 and return the sequence length.
949 To simplify callers of this function, if the blocks match exactly,
950 store the head of the blocks in *F1 and *F2. */
953 flow_find_cross_jump (mode
, bb1
, bb2
, f1
, f2
)
954 int mode ATTRIBUTE_UNUSED
;
955 basic_block bb1
, bb2
;
958 rtx i1
, i2
, last1
, last2
, afterlast1
, afterlast2
;
961 /* Skip simple jumps at the end of the blocks. Complex jumps still
962 need to be compared for equivalence, which we'll do below. */
965 last1
= afterlast1
= last2
= afterlast2
= NULL_RTX
;
967 || (returnjump_p (i1
) && !side_effects_p (PATTERN (i1
))))
975 || (returnjump_p (i2
) && !side_effects_p (PATTERN (i2
))))
978 /* Count everything except for unconditional jump as insn. */
979 if (!simplejump_p (i2
) && !returnjump_p (i2
) && last1
)
987 while (!active_insn_p (i1
) && i1
!= bb1
->head
)
990 while (!active_insn_p (i2
) && i2
!= bb2
->head
)
993 if (i1
== bb1
->head
|| i2
== bb2
->head
)
996 if (!insns_match_p (mode
, i1
, i2
))
999 /* Don't begin a cross-jump with a USE or CLOBBER insn. */
1000 if (active_insn_p (i1
))
1002 /* If the merged insns have different REG_EQUAL notes, then
1004 rtx equiv1
= find_reg_equal_equiv_note (i1
);
1005 rtx equiv2
= find_reg_equal_equiv_note (i2
);
1007 if (equiv1
&& !equiv2
)
1008 remove_note (i1
, equiv1
);
1009 else if (!equiv1
&& equiv2
)
1010 remove_note (i2
, equiv2
);
1011 else if (equiv1
&& equiv2
1012 && !rtx_equal_p (XEXP (equiv1
, 0), XEXP (equiv2
, 0)))
1014 remove_note (i1
, equiv1
);
1015 remove_note (i2
, equiv2
);
1018 afterlast1
= last1
, afterlast2
= last2
;
1019 last1
= i1
, last2
= i2
;
1023 i1
= PREV_INSN (i1
);
1024 i2
= PREV_INSN (i2
);
1028 /* Don't allow the insn after a compare to be shared by
1029 cross-jumping unless the compare is also shared. */
1030 if (ninsns
&& reg_mentioned_p (cc0_rtx
, last1
) && ! sets_cc0_p (last1
))
1031 last1
= afterlast1
, last2
= afterlast2
, ninsns
--;
1034 /* Include preceding notes and labels in the cross-jump. One,
1035 this may bring us to the head of the blocks as requested above.
1036 Two, it keeps line number notes as matched as may be. */
1039 while (last1
!= bb1
->head
&& !active_insn_p (PREV_INSN (last1
)))
1040 last1
= PREV_INSN (last1
);
1042 if (last1
!= bb1
->head
&& GET_CODE (PREV_INSN (last1
)) == CODE_LABEL
)
1043 last1
= PREV_INSN (last1
);
1045 while (last2
!= bb2
->head
&& !active_insn_p (PREV_INSN (last2
)))
1046 last2
= PREV_INSN (last2
);
1048 if (last2
!= bb2
->head
&& GET_CODE (PREV_INSN (last2
)) == CODE_LABEL
)
1049 last2
= PREV_INSN (last2
);
1058 /* Return true iff outgoing edges of BB1 and BB2 match, together with
1059 the branch instruction. This means that if we commonize the control
1060 flow before end of the basic block, the semantic remains unchanged.
1062 We may assume that there exists one edge with a common destination. */
1065 outgoing_edges_match (mode
, bb1
, bb2
)
1070 int nehedges1
= 0, nehedges2
= 0;
1071 edge fallthru1
= 0, fallthru2
= 0;
1074 /* If BB1 has only one successor, we may be looking at either an
1075 unconditional jump, or a fake edge to exit. */
1076 if (bb1
->succ
&& !bb1
->succ
->succ_next
1077 && !(bb1
->succ
->flags
& (EDGE_COMPLEX
| EDGE_FAKE
)))
1078 return (bb2
->succ
&& !bb2
->succ
->succ_next
1079 && (bb2
->succ
->flags
& (EDGE_COMPLEX
| EDGE_FAKE
)) == 0);
1081 /* Match conditional jumps - this may get tricky when fallthru and branch
1082 edges are crossed. */
1084 && bb1
->succ
->succ_next
1085 && !bb1
->succ
->succ_next
->succ_next
1086 && any_condjump_p (bb1
->end
)
1087 && onlyjump_p (bb1
->end
))
1089 edge b1
, f1
, b2
, f2
;
1090 bool reverse
, match
;
1091 rtx set1
, set2
, cond1
, cond2
;
1092 enum rtx_code code1
, code2
;
1095 || !bb2
->succ
->succ_next
1096 || bb1
->succ
->succ_next
->succ_next
1097 || !any_condjump_p (bb2
->end
)
1098 || !onlyjump_p (bb1
->end
))
1101 b1
= BRANCH_EDGE (bb1
);
1102 b2
= BRANCH_EDGE (bb2
);
1103 f1
= FALLTHRU_EDGE (bb1
);
1104 f2
= FALLTHRU_EDGE (bb2
);
1106 /* Get around possible forwarders on fallthru edges. Other cases
1107 should be optimized out already. */
1108 if (FORWARDER_BLOCK_P (f1
->dest
))
1109 f1
= f1
->dest
->succ
;
1111 if (FORWARDER_BLOCK_P (f2
->dest
))
1112 f2
= f2
->dest
->succ
;
1114 /* To simplify use of this function, return false if there are
1115 unneeded forwarder blocks. These will get eliminated later
1116 during cleanup_cfg. */
1117 if (FORWARDER_BLOCK_P (f1
->dest
)
1118 || FORWARDER_BLOCK_P (f2
->dest
)
1119 || FORWARDER_BLOCK_P (b1
->dest
)
1120 || FORWARDER_BLOCK_P (b2
->dest
))
1123 if (f1
->dest
== f2
->dest
&& b1
->dest
== b2
->dest
)
1125 else if (f1
->dest
== b2
->dest
&& b1
->dest
== f2
->dest
)
1130 set1
= pc_set (bb1
->end
);
1131 set2
= pc_set (bb2
->end
);
1132 if ((XEXP (SET_SRC (set1
), 1) == pc_rtx
)
1133 != (XEXP (SET_SRC (set2
), 1) == pc_rtx
))
1136 cond1
= XEXP (SET_SRC (set1
), 0);
1137 cond2
= XEXP (SET_SRC (set2
), 0);
1138 code1
= GET_CODE (cond1
);
1140 code2
= reversed_comparison_code (cond2
, bb2
->end
);
1142 code2
= GET_CODE (cond2
);
1144 if (code2
== UNKNOWN
)
1147 /* Verify codes and operands match. */
1148 match
= ((code1
== code2
1149 && rtx_renumbered_equal_p (XEXP (cond1
, 0), XEXP (cond2
, 0))
1150 && rtx_renumbered_equal_p (XEXP (cond1
, 1), XEXP (cond2
, 1)))
1151 || (code1
== swap_condition (code2
)
1152 && rtx_renumbered_equal_p (XEXP (cond1
, 1),
1154 && rtx_renumbered_equal_p (XEXP (cond1
, 0),
1157 /* If we return true, we will join the blocks. Which means that
1158 we will only have one branch prediction bit to work with. Thus
1159 we require the existing branches to have probabilities that are
1163 && bb1
->frequency
> BB_FREQ_MAX
/ 1000
1164 && bb2
->frequency
> BB_FREQ_MAX
/ 1000)
1168 if (b1
->dest
== b2
->dest
)
1169 prob2
= b2
->probability
;
1171 /* Do not use f2 probability as f2 may be forwarded. */
1172 prob2
= REG_BR_PROB_BASE
- b2
->probability
;
1174 /* Fail if the difference in probabilities is
1176 if (abs (b1
->probability
- prob2
) > REG_BR_PROB_BASE
/ 20)
1179 fprintf (rtl_dump_file
,
1180 "Outcomes of branch in bb %i and %i differs to much (%i %i)\n",
1181 bb1
->index
, bb2
->index
, b1
->probability
, prob2
);
1187 if (rtl_dump_file
&& match
)
1188 fprintf (rtl_dump_file
, "Conditionals in bb %i and %i match.\n",
1189 bb1
->index
, bb2
->index
);
1194 /* Generic case - we are seeing an computed jump, table jump or trapping
1197 /* First ensure that the instructions match. There may be many outgoing
1198 edges so this test is generally cheaper.
1199 ??? Currently the tablejumps will never match, as they do have
1200 different tables. */
1201 if (!insns_match_p (mode
, bb1
->end
, bb2
->end
))
1204 /* Search the outgoing edges, ensure that the counts do match, find possible
1205 fallthru and exception handling edges since these needs more
1207 for (e1
= bb1
->succ
, e2
= bb2
->succ
; e1
&& e2
;
1208 e1
= e1
->succ_next
, e2
= e2
->succ_next
)
1210 if (e1
->flags
& EDGE_EH
)
1213 if (e2
->flags
& EDGE_EH
)
1216 if (e1
->flags
& EDGE_FALLTHRU
)
1218 if (e2
->flags
& EDGE_FALLTHRU
)
1222 /* If number of edges of various types does not match, fail. */
1224 || nehedges1
!= nehedges2
1225 || (fallthru1
!= 0) != (fallthru2
!= 0))
1228 /* fallthru edges must be forwarded to the same destination. */
1231 basic_block d1
= (forwarder_block_p (fallthru1
->dest
)
1232 ? fallthru1
->dest
->succ
->dest
: fallthru1
->dest
);
1233 basic_block d2
= (forwarder_block_p (fallthru2
->dest
)
1234 ? fallthru2
->dest
->succ
->dest
: fallthru2
->dest
);
1240 /* In case we do have EH edges, ensure we are in the same region. */
1243 rtx n1
= find_reg_note (bb1
->end
, REG_EH_REGION
, 0);
1244 rtx n2
= find_reg_note (bb2
->end
, REG_EH_REGION
, 0);
1246 if (XEXP (n1
, 0) != XEXP (n2
, 0))
1250 /* We don't need to match the rest of edges as above checks should be enought
1251 to ensure that they are equivalent. */
1255 /* E1 and E2 are edges with the same destination block. Search their
1256 predecessors for common code. If found, redirect control flow from
1257 (maybe the middle of) E1->SRC to (maybe the middle of) E2->SRC. */
1260 try_crossjump_to_edge (mode
, e1
, e2
)
1265 basic_block src1
= e1
->src
, src2
= e2
->src
;
1266 basic_block redirect_to
;
1267 rtx newpos1
, newpos2
;
1272 /* Search backward through forwarder blocks. We don't need to worry
1273 about multiple entry or chained forwarders, as they will be optimized
1274 away. We do this to look past the unconditional jump following a
1275 conditional jump that is required due to the current CFG shape. */
1277 && !src1
->pred
->pred_next
1278 && FORWARDER_BLOCK_P (src1
))
1279 e1
= src1
->pred
, src1
= e1
->src
;
1282 && !src2
->pred
->pred_next
1283 && FORWARDER_BLOCK_P (src2
))
1284 e2
= src2
->pred
, src2
= e2
->src
;
1286 /* Nothing to do if we reach ENTRY, or a common source block. */
1287 if (src1
== ENTRY_BLOCK_PTR
|| src2
== ENTRY_BLOCK_PTR
)
1292 /* Seeing more than 1 forwarder blocks would confuse us later... */
1293 if (FORWARDER_BLOCK_P (e1
->dest
)
1294 && FORWARDER_BLOCK_P (e1
->dest
->succ
->dest
))
1297 if (FORWARDER_BLOCK_P (e2
->dest
)
1298 && FORWARDER_BLOCK_P (e2
->dest
->succ
->dest
))
1301 /* Likewise with dead code (possibly newly created by the other optimizations
1303 if (!src1
->pred
|| !src2
->pred
)
1306 /* Look for the common insn sequence, part the first ... */
1307 if (!outgoing_edges_match (mode
, src1
, src2
))
1310 /* ... and part the second. */
1311 nmatch
= flow_find_cross_jump (mode
, src1
, src2
, &newpos1
, &newpos2
);
1315 /* Avoid splitting if possible. */
1316 if (newpos2
== src2
->head
)
1321 fprintf (rtl_dump_file
, "Splitting bb %i before %i insns\n",
1322 src2
->index
, nmatch
);
1323 redirect_to
= split_block (src2
, PREV_INSN (newpos2
))->dest
;
1327 fprintf (rtl_dump_file
,
1328 "Cross jumping from bb %i to bb %i; %i common insns\n",
1329 src1
->index
, src2
->index
, nmatch
);
1331 redirect_to
->count
+= src1
->count
;
1332 redirect_to
->frequency
+= src1
->frequency
;
1334 /* Recompute the frequencies and counts of outgoing edges. */
1335 for (s
= redirect_to
->succ
; s
; s
= s
->succ_next
)
1338 basic_block d
= s
->dest
;
1340 if (FORWARDER_BLOCK_P (d
))
1343 for (s2
= src1
->succ
; ; s2
= s2
->succ_next
)
1345 basic_block d2
= s2
->dest
;
1346 if (FORWARDER_BLOCK_P (d2
))
1347 d2
= d2
->succ
->dest
;
1352 s
->count
+= s2
->count
;
1354 /* Take care to update possible forwarder blocks. We verified
1355 that there is no more than one in the chain, so we can't run
1356 into infinite loop. */
1357 if (FORWARDER_BLOCK_P (s
->dest
))
1359 s
->dest
->succ
->count
+= s2
->count
;
1360 s
->dest
->count
+= s2
->count
;
1361 s
->dest
->frequency
+= EDGE_FREQUENCY (s
);
1364 if (FORWARDER_BLOCK_P (s2
->dest
))
1366 s2
->dest
->succ
->count
-= s2
->count
;
1367 if (s2
->dest
->succ
->count
< 0)
1368 s2
->dest
->succ
->count
= 0;
1369 s2
->dest
->count
-= s2
->count
;
1370 s2
->dest
->frequency
-= EDGE_FREQUENCY (s
);
1371 if (s2
->dest
->frequency
< 0)
1372 s2
->dest
->frequency
= 0;
1373 if (s2
->dest
->count
< 0)
1374 s2
->dest
->count
= 0;
1377 if (!redirect_to
->frequency
&& !src1
->frequency
)
1378 s
->probability
= (s
->probability
+ s2
->probability
) / 2;
1381 = ((s
->probability
* redirect_to
->frequency
+
1382 s2
->probability
* src1
->frequency
)
1383 / (redirect_to
->frequency
+ src1
->frequency
));
1386 update_br_prob_note (redirect_to
);
1388 /* Edit SRC1 to go to REDIRECT_TO at NEWPOS1. */
1390 /* Skip possible basic block header. */
1391 if (GET_CODE (newpos1
) == CODE_LABEL
)
1392 newpos1
= NEXT_INSN (newpos1
);
1394 if (GET_CODE (newpos1
) == NOTE
)
1395 newpos1
= NEXT_INSN (newpos1
);
1398 /* Emit the jump insn. */
1399 label
= block_label (redirect_to
);
1400 emit_jump_insn_after (gen_jump (label
), src1
->end
);
1401 JUMP_LABEL (src1
->end
) = label
;
1402 LABEL_NUSES (label
)++;
1404 /* Delete the now unreachable instructions. */
1405 delete_insn_chain (newpos1
, last
);
1407 /* Make sure there is a barrier after the new jump. */
1408 last
= next_nonnote_insn (src1
->end
);
1409 if (!last
|| GET_CODE (last
) != BARRIER
)
1410 emit_barrier_after (src1
->end
);
1414 remove_edge (src1
->succ
);
1415 make_single_succ_edge (src1
, redirect_to
, 0);
1417 BB_SET_FLAG (src1
, BB_UPDATE_LIFE
);
1418 update_forwarder_flag (src1
);
1423 /* Search the predecessors of BB for common insn sequences. When found,
1424 share code between them by redirecting control flow. Return true if
1425 any changes made. */
1428 try_crossjump_bb (mode
, bb
)
1432 edge e
, e2
, nexte2
, nexte
, fallthru
;
1435 /* Nothing to do if there is not at least two incoming edges. */
1436 if (!bb
->pred
|| !bb
->pred
->pred_next
)
1439 /* It is always cheapest to redirect a block that ends in a branch to
1440 a block that falls through into BB, as that adds no branches to the
1441 program. We'll try that combination first. */
1442 for (fallthru
= bb
->pred
; fallthru
; fallthru
= fallthru
->pred_next
)
1443 if (fallthru
->flags
& EDGE_FALLTHRU
)
1447 for (e
= bb
->pred
; e
; e
= nexte
)
1449 nexte
= e
->pred_next
;
1451 /* As noted above, first try with the fallthru predecessor. */
1454 /* Don't combine the fallthru edge into anything else.
1455 If there is a match, we'll do it the other way around. */
1459 if (try_crossjump_to_edge (mode
, e
, fallthru
))
1467 /* Non-obvious work limiting check: Recognize that we're going
1468 to call try_crossjump_bb on every basic block. So if we have
1469 two blocks with lots of outgoing edges (a switch) and they
1470 share lots of common destinations, then we would do the
1471 cross-jump check once for each common destination.
1473 Now, if the blocks actually are cross-jump candidates, then
1474 all of their destinations will be shared. Which means that
1475 we only need check them for cross-jump candidacy once. We
1476 can eliminate redundant checks of crossjump(A,B) by arbitrarily
1477 choosing to do the check from the block for which the edge
1478 in question is the first successor of A. */
1479 if (e
->src
->succ
!= e
)
1482 for (e2
= bb
->pred
; e2
; e2
= nexte2
)
1484 nexte2
= e2
->pred_next
;
1489 /* We've already checked the fallthru edge above. */
1493 /* The "first successor" check above only prevents multiple
1494 checks of crossjump(A,B). In order to prevent redundant
1495 checks of crossjump(B,A), require that A be the block
1496 with the lowest index. */
1497 if (e
->src
->index
> e2
->src
->index
)
1500 if (try_crossjump_to_edge (mode
, e
, e2
))
1512 /* Do simple CFG optimizations - basic block merging, simplifying of jump
1513 instructions etc. Return nonzero if changes were made. */
1516 try_optimize_cfg (mode
)
1520 bool changed_overall
= false;
1525 if (mode
& CLEANUP_CROSSJUMP
)
1526 add_noreturn_fake_exit_edges ();
1528 for (i
= 0; i
< n_basic_blocks
; i
++)
1529 update_forwarder_flag (BASIC_BLOCK (i
));
1531 /* Attempt to merge blocks as made possible by edge removal. If a block
1532 has only one successor, and the successor has only one predecessor,
1533 they may be combined. */
1540 fprintf (rtl_dump_file
, "\n\ntry_optimize_cfg iteration %i\n\n",
1543 for (i
= 0; i
< n_basic_blocks
;)
1545 basic_block c
, b
= BASIC_BLOCK (i
);
1547 bool changed_here
= false;
1549 /* Delete trivially dead basic blocks. */
1550 while (b
->pred
== NULL
)
1552 c
= BASIC_BLOCK (b
->index
- 1);
1554 fprintf (rtl_dump_file
, "Deleting block %i.\n", b
->index
);
1556 flow_delete_block (b
);
1561 /* Remove code labels no longer used. Don't do this before
1562 CALL_PLACEHOLDER is removed, as some branches may be hidden
1564 if (b
->pred
->pred_next
== NULL
1565 && (b
->pred
->flags
& EDGE_FALLTHRU
)
1566 && !(b
->pred
->flags
& EDGE_COMPLEX
)
1567 && GET_CODE (b
->head
) == CODE_LABEL
1568 && (!(mode
& CLEANUP_PRE_SIBCALL
)
1569 || !tail_recursion_label_p (b
->head
))
1570 /* If the previous block ends with a branch to this block,
1571 we can't delete the label. Normally this is a condjump
1572 that is yet to be simplified, but if CASE_DROPS_THRU,
1573 this can be a tablejump with some element going to the
1574 same place as the default (fallthru). */
1575 && (b
->pred
->src
== ENTRY_BLOCK_PTR
1576 || GET_CODE (b
->pred
->src
->end
) != JUMP_INSN
1577 || ! label_is_jump_target_p (b
->head
, b
->pred
->src
->end
)))
1579 rtx label
= b
->head
;
1581 b
->head
= NEXT_INSN (b
->head
);
1582 delete_insn_chain (label
, label
);
1584 fprintf (rtl_dump_file
, "Deleted label in block %i.\n",
1588 /* If we fall through an empty block, we can remove it. */
1589 if (b
->pred
->pred_next
== NULL
1590 && (b
->pred
->flags
& EDGE_FALLTHRU
)
1591 && GET_CODE (b
->head
) != CODE_LABEL
1592 && FORWARDER_BLOCK_P (b
)
1593 /* Note that forwarder_block_p true ensures that there
1594 is a successor for this block. */
1595 && (b
->succ
->flags
& EDGE_FALLTHRU
)
1596 && n_basic_blocks
> 1)
1599 fprintf (rtl_dump_file
, "Deleting fallthru block %i.\n",
1602 c
= BASIC_BLOCK (b
->index
? b
->index
- 1 : 1);
1603 redirect_edge_succ_nodup (b
->pred
, b
->succ
->dest
);
1604 flow_delete_block (b
);
1609 /* Merge blocks. Loop because chains of blocks might be
1611 while ((s
= b
->succ
) != NULL
1612 && s
->succ_next
== NULL
1613 && !(s
->flags
& EDGE_COMPLEX
)
1614 && (c
= s
->dest
) != EXIT_BLOCK_PTR
1615 && c
->pred
->pred_next
== NULL
1616 /* If the jump insn has side effects,
1617 we can't kill the edge. */
1618 && (GET_CODE (b
->end
) != JUMP_INSN
1619 || onlyjump_p (b
->end
))
1620 && merge_blocks (s
, b
, c
, mode
))
1621 changed_here
= true;
1623 /* Simplify branch over branch. */
1624 if ((mode
& CLEANUP_EXPENSIVE
) && try_simplify_condjump (b
))
1626 BB_SET_FLAG (b
, BB_UPDATE_LIFE
);
1627 changed_here
= true;
1630 /* If B has a single outgoing edge, but uses a non-trivial jump
1631 instruction without side-effects, we can either delete the
1632 jump entirely, or replace it with a simple unconditional jump.
1633 Use redirect_edge_and_branch to do the dirty work. */
1635 && ! b
->succ
->succ_next
1636 && b
->succ
->dest
!= EXIT_BLOCK_PTR
1637 && onlyjump_p (b
->end
)
1638 && redirect_edge_and_branch (b
->succ
, b
->succ
->dest
))
1640 BB_SET_FLAG (b
, BB_UPDATE_LIFE
);
1641 update_forwarder_flag (b
);
1642 changed_here
= true;
1645 /* Simplify branch to branch. */
1646 if (try_forward_edges (mode
, b
))
1647 changed_here
= true;
1649 /* Look for shared code between blocks. */
1650 if ((mode
& CLEANUP_CROSSJUMP
)
1651 && try_crossjump_bb (mode
, b
))
1652 changed_here
= true;
1654 /* Don't get confused by the index shift caused by deleting
1662 if ((mode
& CLEANUP_CROSSJUMP
)
1663 && try_crossjump_bb (mode
, EXIT_BLOCK_PTR
))
1666 #ifdef ENABLE_CHECKING
1668 verify_flow_info ();
1671 changed_overall
|= changed
;
1675 if (mode
& CLEANUP_CROSSJUMP
)
1676 remove_fake_edges ();
1678 if ((mode
& CLEANUP_UPDATE_LIFE
) && changed_overall
)
1682 blocks
= sbitmap_alloc (n_basic_blocks
);
1683 sbitmap_zero (blocks
);
1684 for (i
= 0; i
< n_basic_blocks
; i
++)
1685 if (BB_FLAGS (BASIC_BLOCK (i
)) & BB_UPDATE_LIFE
)
1688 SET_BIT (blocks
, i
);
1692 update_life_info (blocks
, UPDATE_LIFE_GLOBAL
,
1693 PROP_DEATH_NOTES
| PROP_SCAN_DEAD_CODE
1694 | PROP_KILL_DEAD_CODE
);
1695 sbitmap_free (blocks
);
1698 for (i
= 0; i
< n_basic_blocks
; i
++)
1699 BASIC_BLOCK (i
)->aux
= NULL
;
1701 return changed_overall
;
1704 /* Delete all unreachable basic blocks. */
1707 delete_unreachable_blocks ()
1710 bool changed
= false;
1712 find_unreachable_blocks ();
1714 /* Delete all unreachable basic blocks. Count down so that we
1715 don't interfere with the block renumbering that happens in
1716 flow_delete_block. */
1718 for (i
= n_basic_blocks
- 1; i
>= 0; --i
)
1720 basic_block b
= BASIC_BLOCK (i
);
1722 if (!(b
->flags
& BB_REACHABLE
))
1723 flow_delete_block (b
), changed
= true;
1727 tidy_fallthru_edges ();
1731 /* Tidy the CFG by deleting unreachable code and whatnot. */
1737 bool changed
= false;
1739 timevar_push (TV_CLEANUP_CFG
);
1740 changed
= delete_unreachable_blocks ();
1741 if (try_optimize_cfg (mode
))
1742 delete_unreachable_blocks (), changed
= true;
1744 /* Kill the data we won't maintain. */
1745 free_EXPR_LIST_list (&label_value_list
);
1746 free_EXPR_LIST_list (&tail_recursion_label_list
);
1747 timevar_pop (TV_CLEANUP_CFG
);